1. Field of the Invention
The present invention relates to a fuel cell stack, and more particularly, to a heat transfer structure for the fuel cell stack.
2. Description of the Related Technology
As is well known in the related art, a fuel cell is an energy generating system for directly transforming chemical reaction energy of a fuel and a separate oxidizing agent into electrical energy. The fuel cell may be classified variously according to types of system components and fuels.
The fuel cell includes a stack formed by successively stacking a plurality of unit cells. In addition, the fuel cell (hereinafter referred to as a fuel cell stack) generates electrical energy by providing the fuel and the oxidizing agent to the unit cells.
In the conventional fuel cell stack, the unit cells generate heat of a predetermined temperature through a reduction reaction of the oxidizing agent. The fuel cell stack generating the heat may be cooled down to a temperature range corresponding to a specific operating temperature range of the stack by circulating cooling air or cooling water into the stack.
However, in the conventional fuel cell stack, there occurs a temperature difference in the overall stack due to a characteristic structure of successively stacking the unit cells, a concentration/pressure difference of the fuel and the oxidizing agent, or a utilization coefficient of the fuel.
In other words, in the conventional fuel cell stack, the unit cells located in the central portion show a high heat-generating temperature, and the unit cells located in the outside of the central portion show a low heat-generating temperature.
A non-uniform temperature distribution of the fuel cell stack as described above causes deterioration in performance of the fuel cell stack such as difficulty in outputting a constant voltage through the unit cells of the stack.